LONDON (SHARECAST) - (ShareCast News) - London's FTSE 250 was down 0.5% to 19,690.73 in afternoon trade as investors mulled over weaker-than-expected construction sector data.Victrex racked up strong gains as it said its effective tax rate under Patent Box - which enables companies to apply a lower rate of corporation tax to profit earned after 1 April 2013 to its patented inventions - is expected to drop to around 12% from 21%. This will in turn have an ongoing favourable impact on earnings per share and cash, although no cash benefit would be seen in FY17.

Hochschild Mining and Centamin were boosted by gold prices, which rallied to 11-month highs on the back of worries about North Korea's hydrogen bomb test over the weekend.

Indivior was clawing back some gains, having tanked at the end of last week as it said there was a "material" risk to revenue after a US court ruled that a generic version of its Suboxone film to treat opioid addiction by Dr Reddy's does not infringe any of the London-listed company's patents. Indivior- for whom Suboxone represented around 80% of revenue last year - is set to appeal the decision.

Acacia Mining was in the red after saying it expects to return to positive cash generation early in 2018 after it stopped underground mining at one of its three Tanzanian mines amid an ongoing government ban on metal concentrate exports.

Business-to-business information company Ascential retreated after Peel Hunt downgraded the stock to 'hold'.